1. Field of the Invention
The present invention relates to a production control apparatus which controls actual production information in a production line and a production system provided with the same.
2. Description of the Related Art
In a machine factory, a production line in which a plurality of manufacturing machines such as machine tools or robots are arranged is built. If it is found that a product shipped through a production line is defective, a cause of defect can be surveyed extending back to the production process of the product. Specifically, in each manufacturing machine, the traceability is collected and stored in a database.
The traceability data means data which may affect the manufacturing quality, such as current values of motors for the machine tools or robots, etc., during machining, time required for machining, alarm information generated during machining, programs or parameters used during machining, identification numbers of tools used for machining, ambient temperature during machining, or a machining error measured by a measuring device after machining. In the case where the production line is formed by operators, information such as contents of operations, check results or measurements after operation, or ID numbers of the tools used, etc. is traceability data.
Such traceability data is stored in the database, together with ID numbers of the manufacturing machines or operators, product numbers, and dates of manufacture, etc. (see WO 2013/111324). If there is a defective product found among collected products, the date of manufacture of the defective product, and the manufacturing machine which was used to manufacture the defective product or the operator by whom the defective product was produced, are identified. Thereafter, the traceability data at the time when the defective product was produced is identified based on the specified date of manufacture or the ID number of the specified manufacturing machine or operator.
However, in the production line in which identical products are mass-produced, there is a large number of products produced by the same manufacturing machine or operator on the same date of manufacture, and accordingly, it is difficult to accurately identify the traceability data at the time when the defective product was manufactured. Namely, it is necessary to analyze the traceability data of all of the products that can be considered to have been produced on the date of manufacture on which the defective product was produced, and this makes it very difficult to discover the reason why the defective product was produced.
Under these circumstances, there has been a need of setting identification information for each product and administrating the traceability data for each product. To this end, Japanese Patent Application Publication No. 2004-355534 discloses a method for storing machining and assembling information of individual workpieces in association with the unique ID (identifier) of each workpiece in machining equipment.
More specifically, in the method disclosed in Japanese Patent Application Publication No. 2004-355534, an ID tag having an IC memory incorporated therein is attached to each workpiece beforehand and the traceability data is recorded in the IC memory each time the workpiece is machined and assembled. When a series of machining and assembling processes of the workpieces are finished to manufacture products, bar codes are attached to the individual products to allocate the ID numbers, and thereafter, the ID tags are removed from the products. The traceability data is read out from the removed ID tags and is stored in a storage device of a host computer in association with the ID numbers of the products. Thus, if a defective product is found from among the shipped products, the ID number of the defective product is read out from the bar code attached to the defective product and is inputted to the host computer, whereby the traceability corresponding to the ID information of the defective product can be retrieved.
However, the method disclosed in Japanese Patent Application Publication No. 2004-355534 has the following drawbacks.
It is impossible to record the traceability data more than the capacity of the IC memory incorporated in the ID tag.
When the products are mass-produced, it is necessary to prepare a large number of ID tags, thus resulting in an increase in cost.
As it is necessary to attach the ID tags to the workpieces during the manufacturing process from the commencement of machining of the workpieces to the completion of the products, the workpieces must be those which can be machined and assembled with the ID tags attached thereto.
When a product is completed by assembling a plurality of workpieces during the manufacturing process, the ID tag on which the traceability data is to be recorded is ambiguous among the ID tags individually attached to the plurality of workpieces assembled. Moreover, the ID tag having the traceability data recorded thereon cannot be removed from the workpiece without disassembling the product.